1. Technical Field
The present invention relates to a system for optically inspecting the surface of moving sheets of material. More particularly, the present invention relates to a system for optically inspecting high velocity individual sheets spaced from each other and having scrolled or unscrolled edges in a production line.
2. Statement of the Problem
In the manufacture of metal containers (such as steel beverage containers), the containers and container ends are stamped from metal sheets. These sheets may be coated, printed upon, or otherwise treated in accordance with the specifications for the desired container. In a sheet coating and decorating production line, the sheets move at high velocities such as 500 feet per minute. At such high velocities, it is impractical to have a person visually scan each sheet to ascertain the presence of defects.
A need, therefore, exists for an automatic optical inspection system and method for optically inspecting the surface of each sheet, at production line velocities, and to reject sheets with unacceptably sized defects from the production line without interfering with the delivery of sheets in the production line.
Since these sheets may have either scrolled or unscrolled edges depending upon the desired specifications, a need further exists for a system and a method which performs automatic optical inspection of each individual sheet whether or not the sheet has scrolled edges. A need further exists for a system and a method to optically inspect the total surface of the sheet including the scrolled edges.
A need also exists for a system and method which performs the optical inspection of the sheets regardless of the spacings between the individual sheets and regardless of the velocity that the sheets are moving in the production line.
Finally, a need exists to provide for the optical inspection of sheets that may be skewed and otherwise misaligned within predetermined amounts as the sheets travel through the production line.